Goodbye California - Alistair [1]
Nevertheless, it had been destroyed by an earthquake the epicentre of which had been some eight miles distant to the north-east. But what was important – and significant – about the earthquake that had caused this considerable damage was the factor of its power – or lack of it. The power, or magnitude, of an earthquake is registered on an arbitrarily chosen Richter scale which ranges from zero to twelve. And what is important to bear in mind is that the Richter scale progresses not arithmetically but logarithmically. Thus, a six on the Richter scale is ten times as powerful as a five or a hundred times as powerful as a four. The San Fernando earthquake which levelled this hospital block in Sylmar registered six-point-three on the Richter scale: the one that wreaked havoc on San Francisco in 1906 registered seven-point-nine (according to the recent modifications of the Richter scale). Thus, the earthquake that caused this damage in Sylmar was possessed of only one per cent of the effective power of the San Francisco one. It is a sobering and, to those burdened with an over-active imagination, a fearful reflection.
What is even more sobering and frightening is the fact that, to the best of our knowledge, no great earthquake – ‘great’ is arbitrarily taken to be anything eight and above on the Richter scale – has ever occurred beneath or in the immediate vicinity of any major city. (Such a disaster may have occurred in that awesome North Chinese earthquake of 1976 when a third of a million people are reported to have died: but the Chinese have dropped a total news blanket over this tragedy.) But the law of averages would indicate strongly that somewhere, some time, a major earthquake will occur in a place which is not conveniently uninhabited or, at least, sparsely populated. There is no reason not to imagine, unless one chooses to take refuge behind I-don’t-want-to-know mental blinkers, that this possibility may even today be a probability.
The word ‘probability’ is used because the law of averages is strengthened by the fact that with the exception of China, Turkey and, to a lesser extent, Italy, earthquakes largely tend to take place in coastal areas, whether those coastal areas be of land masses or islands; and it is in those coastal areas, for the purposes of trade and because they are the points in ingress to the hinterland, that many of the world’s great cities have been built. Tokyo, Los Angeles and San Francisco are three such examples.
That earthquakes should be largely confined to those areas is in no way fortuitous: their cause, as well as that of volcanoes, is now a matter of almost universal agreement among geologists. The theory is simply that in the unimaginably distant past when land first appeared it was in the form of one gigantic super-continent surrounded by – inevitably – one massive ocean. With the passage of time and for reasons not yet definitely ascertained this super-continent broke up into several different continental masses, which, borne on what are called their ‘tectonic plates’ – which float on the still molten magma layer of the earth – drifted apart. Those tectonic plates occasionally bang or rub against one another; the effects of the collisions are transmitted either to the land above or the ocean floor and appear in the form of earthquakes or volcanoes.
Most of California lies on the North American plate which, while tending to move westward, is not the real villain of the piece. That unhappy distinction belongs to that same North Pacific plate which deals so hardly with China, Japan and the Philippines and on which that section of California lying to the west of the San Andreas Fault so unhappily lies. Although the North Pacific plate appears to be rotating slightly, its movement in California is still roughly to the north-west and, now